Leonidas, a runner who competed between 164 and 152 BC according to Olympic historians, is the only other athlete to have won 12 solo titles.

There is plenty of documentary evidence to attest to the dominance of Phelps, winner of a record 21 golds and 25 medals in an astonishing career spanning five Games that is far from finished.

The achievements of Leonidas rely on somewhat sketchier accounts, provided much later by Philostratus the Athenian and Pausanias who hailed the runner's 12 victories through four Olympiads.

The sentiments expressed by Phelps in the early hours of Wednesday after winning the 200m butterfly title would surely have resonated with Leonidas, even if the Greek had to compete with a shield and helmet.

"That's a lot of medals," grinned the American. "We got a lot of medals. It's just insane. It's mind-blowing."

Phelps has by far the most of any Olympic athlete and is the only one to win eight golds at a single Games, an achievement that earned much fanfare plus a $1 million bonus in Beijing in 2008.